The diagnosis and treatment of chronic pain is extremely difficult because, in the absence of more objective signs, the practitioner must rely heavily upon the patient's sometimes idiosyncratic definition of pain and suffering. The studies proposed here will validate the use of recently developed individual differences, multidimensional scaling (MDS) techniques, which promise to quantify the nature of the patient's pain and suffering far better than previous techniques. These procedures map the underlying structure of the patients' pain/suffering complaint, and then determine the coordinates of each person on these dimensions to generate the Individual Pain/Suffering (IP/S) Profile. Study 1 will use 278 descriptors of pain and suffering (and their opposites) to generate the pain/suffering spaces for 6 groups of healthy volunteers: Black, Hispanic, Caucasian, male and female, to test whether this spatial structure is appropriate for use in the general population. In addition, redundant, unstable, and irrelevant descriptors will be winnowed out, leaving a clinically more manageable set of approximately 100 items. We will also determine whether continuous dimensions or discrete clusters (or both) best describe the structure of pain/suffering space. These items will be used in Study 2, where another stratified sample will be used to study the sensitivity of the IP/S Profile to the differential effects of pain (electrical stimulation) and psychological distress (medical illustrations). Retest reliability of the 100 descriptors will be determined. In Study 3, outpatients suffering back and other chronic pain syndromes will be compared. The power of the IP/S Profile to make differential diagnoses and predict treatment outcome will be compared to that of the McGill Pain Questionnaire. To evaluate the diagnostic potential of MDS, chronic patients will be used to create standard Syndrome Profiles for a variety of illnesses. These "templates' will then be used to diagnose atypical patients. In Study 4, women suffering premenstrual syndrome will be compared with and without noxious electrical stimulation during normal and stressful days of their cycle, to test the hypothesis that the IP/S Profile coordinates for pain are independent of the coordinates for emotional state. In Study 5, the effects of intravenous Fentanyl, Diazepam, and saline will be studied under neutral and noxious electrical stimulation conditions; the pain space should remain relatively constant, but the IP/S Profile should reflect the known analgesic and anxiolytic properties of these drugs. These studies are expected to lay the groundwork for a reliable and valid instrument to replace the present, but inadequate, standard of pain assessment, the McGill Pain Questionnaire.